3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Stephane Eranian <eran...@google.com>
commit 1d9d8639c063caf6efc2447f5f26aa637f844ff6 upstream.
This patch fixes a kernel crash when using precise sampling (PEBS)
after a suspend/resume. Turns out the CPU notifier code is not invoked
on CPU0 (BP). Therefore, the DS_AREA (used by PEBS) is not restored properly
by the kernel and keeps it power-on/resume value of 0 causing any PEBS
measurement to crash when running on CPU0.
The workaround is to add a hook in the actual resume code to restore
the DS Area MSR value. It is invoked for all CPUS. So for all but CPU0,
the DS_AREA will be restored twice but this is harmless.
Reported-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Stephane Eranian <eran...@google.com>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
arch/x86/kernel/cpu/perf_event_intel_ds.c | 8 ++++++++
arch/x86/power/cpu.c | 2 ++
include/linux/perf_event.h | 2 ++
3 files changed, 12 insertions(+)
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -736,3 +736,11 @@ void intel_ds_init(void)
}
}
}
+
+void perf_restore_debug_store(void)
+{
+ if (!x86_pmu.bts && !x86_pmu.pebs)
+ return;
+
+ init_debug_store_on_cpu(smp_processor_id());
+}
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -11,6 +11,7 @@
#include <linux/suspend.h>
#include <linux/export.h>
#include <linux/smp.h>
+#include <linux/perf_event.h>
#include <asm/pgtable.h>
#include <asm/proto.h>
@@ -225,6 +226,7 @@ static void __restore_processor_state(st
do_fpu_end();
mtrr_bp_restore();
+ perf_restore_debug_store();
}
/* Needed by apm.c */
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1146,6 +1146,7 @@ extern void perf_swevent_put_recursion_c
extern void perf_event_enable(struct perf_event *event);
extern void perf_event_disable(struct perf_event *event);
extern void perf_event_task_tick(void);
+extern void perf_restore_debug_store(void);
#else
static inline void
perf_event_task_sched_in(struct task_struct *prev,
@@ -1184,6 +1185,7 @@ static inline void perf_swevent_put_recu
static inline void perf_event_enable(struct perf_event *event) { }
static inline void perf_event_disable(struct perf_event *event)
{ }
static inline void perf_event_task_tick(void) { }
+static inline void perf_restore_debug_store(void) { }
#endif
#define perf_output_put(handle, x) perf_output_copy((handle), &(x), sizeof(x))
--
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